A folding apparatus of the general type to which the subject invention is directed comprises a cylinder characterized as a folding blade cylinder or a collect cylinder, which cylinder supports a multitude of holding tools around its periphery that are usable for securing a printed product that is fed to the cylinder and is to be folded. A plurality of folding blades, which extend outward from the interior of the cylinder, engage a printed product, which is held against the cylinder. These folding blades engage the printed product along a predetermined fold line for the printed product, and thereby press it into a folding jaw of a folding jaw cylinder that functions in coordination with the folding blade or collect cylinder. In non-collect operation, each time a printed product passes through the gap between the folding blade cylinder and the folding jaw cylinder, the printed product is released by its holding tool and the subsequent folding blade is extended. During collect operation, a printed product that is held on the folding cylinder passes through the gap at least 2 or n times. During each revolution of the folding cylinder, another printed product is collected on the same peripheral segment of the folding cylinder. Ultimately, printed products, which are collected n times, are pushed together onto the folding jaw cylinder and are thereby folded.
The movement of the holding tools and of the folding blades is generally determined by a control cam, the contour of which control cam is traced by a multitude of cam follower rolls, each of which is coupled to one of the holding tools or to the folding blade.
In a first type of folding apparatus, the control cam is formed by two disks that are mounted coaxially relative to the cylinder, and which are characterized as a cam disk and as a cover disk, which cam disk and cover disk are traced simultaneously by the cam and cover disk follower rolls. The cam disk, which is typically stationary, is equipped with a recessed area, into which a follower roll can dip. When this occurs, the tool that is controlled by the follower roll executes a working movement. In the case of a holding tool, this movement may be, for example, the release of a printed product, or in the case of a folding blade, the working movement may be an extension of the blade.
The cover disk is also equipped with at least one recessed area. This at least one recessed area is positioned during non-collect operation of the folding blade cylinder such that it overlaps the recessed area of the cam disk and thus does not prevent the follower roll from dipping into it. The cover disk can be stationary or can rotate. During collect operation of the folding blade cylinder, the cover disk rotates at a speed that is different from the rotational speed of the cylinder. The recessed areas of the two disks overlap, and the working movement is executed only with every nth revolution of the cylinder. The result is that n collected printed products are then transferred and are folded at the same time.
To achieve the greatest possible flexibility in production, it is desirable to be able to adjust any random value for n, up to an upper limit of nmax. Since, in order to vary n, in general only the phase position between the cam disk and the cover disk can be adjusted, both nmax and the number of possible values for n are relatively small.
To achieve greater variability for collect operation, a folding apparatus has been proposed in DE 38 28 372 A1, in which the cover disk is replaced by a multitude of radially adjustable covering cams. These covering cams make it possible, to a certain extent, to form a cover disk having a circumferential shape that can be adjusted based upon the desired value for n.
With this previously known folding apparatus, eight covering cams are provided, which eight covering cams form two diametrically opposite groups of four each, and which are distributed over an angular interval of 90°. Within a group, the angular distances between the covering cams amount to 30°, 15° and 45°, in sequence. The folding cylinder is comprised of seven parts. With two different rotational speeds for the covering cams relative to the cylinder, production modes in which n=1, 2, 3, 4, or in other words, non-collect, single-collect, double-collect and triple-collect production modes can be realized.